Packaging method and packaging apparatus

ABSTRACT

The invention provide an apparatus that can seal with film an article placed on a tray without having to change tooling for each shape and size of tray. 
     Packaging apparatus  1  covers opening o with film Fm and thermally welds film Fm to flange f. Tray T is provided with flange f and opening o surrounded by flange f on its upper face. The apparatus is provided with roller  3  and roller swivel mechanism  8 . Roller  3  can touch against film Fm on a portion of flange f. The touched surface of roller  3  is at an angle with respect to a horizontal plane. Roller swivel mechanism  8  moves roller  3  in a swiveling manner.

TECHNICAL FIELD

The present invention relates to a packaging method and packagingapparatus. More particularly, the present invention relates to apackaging method and packaging apparatus wherein a tray, having a flangeand an opening surrounded by said flange on its upper face andcontaining an article to be packaged, is covered with a film over theopening and the film is welded to the flange.

BACKGROUND ART

Conventionally fresh fish and meat, as well as side dishes and otherprocessed foods, have been packaged using the “overlap method.” Theoverlap method involves putting the food product into a tray andwrapping the entire tray with a film.

Consequently, the planar size of the film must be several times largerthan the planar size of the tray because both the tray and the entirefood product must be covered and the ends of the film must overlap inorder to form a seal. Furthermore, such packages are often sealed bypressing a hot plate against the overlapped ends of the film on thebottom of the tray, which results in an inferior seal.

Meanwhile, there are some cases where another method (hereinafter calledthe “top-seal method”) is used instead of the overlap method. With thetop-seal method, the film is placed only over the opening provided inthe upper face of the tray and the film is thermally welded to the trayalong the periphery of the hole. Using the top-seal method can reducefilm consumption by half in comparison with the overlap method.

The top-seal method has been used chiefly for packaging shimeji andother varieties of mushroom. One common form of the top-seal method isto apply an adhesive to the sides of the tray around the opening andbond the ends of the film to the tray when the film is placed over theopening. Another common form is to sandwich the tray and a piece of filmthat is larger than the planar size of the tray between two tools andapply pressure and heat to thermally weld the film to the tray.

The disadvantage with both of these top-seal methods is that theyrequire tooling matched to the size and shape of the tray. Consequently,industries that need to use multiple tray types to package a variety ofdifferent articles often use the overlap method instead of the top-sealmethod. Although the top-seal method provides such merits as reducedfilm consumption and improved sealing characteristics, it is oftenimpractical because a separate set of tools must be prepared for eachdifferent size and shape of tray.

DISCLOSURE OF INVENTION

The object of the present invention is to provide a packaging method andcorresponding packaging apparatus that allow an article placed on a trayto be sealed with a film using the top-seal method but do not requirethe preparation of tooling for each different size and shape of tray.

A packaging method in accordance with the first aspect of the inventionis provided with first, second, third, and fourth steps. In the firststep, the article to be packaged is put on a tray having an opening inits upper face; in the second step, the opening in the tray is coveredwith a film; in the third step, a heated hot member is touched, in adirection intersecting with a vertical direction, against the film on aportion of the tray near the opening where the film touches; and in thefourth step, at least one of the hot member or the tray is moved.

More specifically, in the first step of the packaging method describedin the first aspect, a food product or other article is placed on atray. In the second step, the opening in the upper face of the tray iscovered with a film so that the film is touching a portion of theperiphery of the tray opening. In the third step, the film on a portionof the tray near the opening where the film touches is pressed with aheated hot member in a direction intersecting with a vertical direction.In other words, the hot member is applied at an angle to a portion ofthe tray near the opening. In the fourth step, at least one of the hotmember or the tray is moved while the hot member being applied at anangle to a portion of the tray near the opening. As a result, the entireportion of the film that is touching the tray in the area surroundingthe opening is thermally welded to the tray.

With this method, since at least one of the hot member or the tray ismoved, the hot member and the periphery of the tray opening are movedrelative to each other. Consequently, various shapes and sizes of traycan be accommodated so long as the size of the tray is within certainlimits. Unlike conventional top-seal methods, it is not necessary toprepare tools for each different type of tray or to spend time changingthose tools each time a different tray is used. Therefore, equipmentcosts can be reduced and the efficiency of packaging operations can beimproved.

Also, since the hot member is applied to a portion of the tray near theopening from a direction that intersects with a vertical direction, thehot member only comes in contact with a portion of the tray near theopening and does not come in contact with the portion of the filmcovering the tray opening. Consequently, the portion of the film thatcovers the opening is less likely to melt or develop tiny holes.

It is preferred that a pressure applying mechanism and controller beprovided so that the pressure at which the hot member is applied to aportion of the tray near the opening and the speed at which the hotmember and the periphery of the tray opening are moved relative to eachother can be set to levels that are well matched to the materials fromwhich the tray and film are made. It is also preferred that a controllerand an angle adjustment mechanism be provided so that the degree towhich the heating means heats the hot member and the angle at which thehot member is touched against the portion of the tray near the openingcan be adjusted as necessary and appropriate.

A packaging method in accordance with the second aspect of the inventionis a method as recited in the first aspect, wherein, either one or twoor more hot members are touched against the film on a portion of thetray near the opening in the third step and either one or two or morehot members move along the periphery of the opening in the tray in thefourth step.

By touching two or more hot members against a portion of the tray nearthe opening, the amount by which each hot member must be moved along theperiphery of the tray opening can be reduced in comparison with amountof movement required when only one hot member is used. That is, whenonly one hot member is used, the hot member must be moved at least onefull revolution around the tray opening in order to weld the film to theentire periphery of the tray opening. But, when two or more hot membersare used, the film can be welded to the entire periphery of the trayopening without moving each hot member a full revolution around the trayopening. Thus, the time required to move in the fourth step can bereduced and the efficiency of the packaging process can be improved.

Conversely, costs can be reduced when only one hot member is applied toa portion of the tray near the opening because, although the hot membermust be moved at least one full revolution around the tray opening inorder to weld the film to the entire periphery of the tray opening,fewer hot members need to be prepared.

A packaging method in accordance with the third aspect of the inventionis a method as recited in the first or second aspect, wherein, duringthe third and fourth steps, the hot member not only thermally welds thefilm to a portion of the tray near the opening but also cuts the outerportion of the thermally welded film.

This method improves the efficiency of the packaging process because thefilm is welded and cut simultaneously.

It is also feasible to thermally cut the outer portion of the thermallywelded film by using the hot member that welds the film to the tray. Thehot member can thermally cut the film more reliably if a tensile forceis applied to the film.

A packaging method in accordance with the fourth aspect of the inventionis a method as recited in any one of the first through third aspects,wherein, during the fourth step, the hot member rolls as it moves alongthe periphery of the opening in the tray.

With this method, the frictional resistance between the hot member andthe film on the tray is reduced because the hot member rolls on the tray(i.e., the hot member rotates as it moves along the tray). As a result,the film is less likely to melt or develop tiny holes.

Also, it is preferable for the face of the hot member that contacts thefilm to be made of a resilient material (such as resin or syntheticrubber) so that firm contact can be maintained between the film and thetray even when small irregularities exist on the surface of the tray.

A packaging method in accordance with the fifth aspect of the inventionis a method as recited in any one of the first through fourth aspects,wherein, during the fourth step, the hot member is moved along theperiphery of the opening in the tray by swiveling the hot member about aswivel shaft while planarly moving the swivel shaft.

A packaging method in accordance with the sixth aspect of the inventionis a method as recited in any one of the first through fifth aspects ofthe invention. In the third step, a plurality of the hot members istouched against the periphery of the opening in the tray from above thestretch film. In the fourth step, the hot members are moved along theperiphery of the opening in the tray by swiveling the plurality of hotmembers about the axes of at least two swivel shafts disposed indifferent planar positions.

A packaging apparatus in accordance with the seventh aspect of theinvention is an apparatus, wherein a tray, provided with a flange and anopening surrounded by said flange on its upper face and containing anarticle to be packaged, is covered with a film over the opening and thefilm is welded to the flange. The packaging apparatus is provided with ahot member and a moving means. The hot member is capable of touchingagainst the film on a portion of the flange of the tray, and the face ofthe hot member is capable of touching the tray is at an angle withrespect to a horizontal plane. The moving means moves at least one ofthe hot member or the tray.

With the packaging apparatus described in the seventh aspect of theinvention, the film is thermally welded to the flange by touching thehot member against the film on a portion of the flange of the tray.Then, when the hot member and the tray are moved relative to each otherby the moving means, the hot member touches all portions of the flangeand the film is thermally welded to the entire flange.

With this apparatus, since the hot member touches a portion of theflange and at least one of the hot members or the tray is moved, variousshapes and sizes of tray can be accommodated so long as the size of thetray is within certain limits. Unlike conventional top-seal methods, itis not necessary to prepare tools for each different type of tray or tospend time changing those tools each time a different tray is used.Therefore, equipment costs can be reduced and the efficiency ofpackaging operations can be improved.

Also, since the face of the hot member is capable of touching the trayis at an angle with respect to a horizontal plane, the hot member onlycomes in contact with the flange of the tray and does not come incontact with the portion of the film covering a opening surrounded bythe flange. Consequently, the portion of the film that covers theopening is less likely to melt or develop tiny holes.

A packaging apparatus in accordance with the eighth aspect of theinvention is an apparatus as recited in the seventh aspect, wherein, themoving means moves the hot member against the tray.

A packaging apparatus in accordance with the ninth aspect of theinvention is an apparatus as recited in the eighth aspect, wherein themoving means is provided with a swivel mechanism and a moving swivelshaft mechanism. The swivel mechanism swivels the hot member about aswivel shaft. The moving swivel shaft mechanism planarly moves theswivel shaft of the swivel mechanism.

With this apparatus, the swivel mechanism and the moving swivel shaftmechanism move the hot member. The moving swivel shaft mechanism canremain still when packaging trays with circular planar shapes or it canbe operated when packaging trays with a large length-to-width ratio (orlarge rectangular trays). When the moving swivel shaft mechanism is usedto move the swivel shaft while the hot member is being swiveled, shapes(and sizes) of tray that the hot member cannot follow using swivelingalone can be accommodated. That is, by combining movement of the swivelshaft with swiveling, the hot member can be moved along the entireflange of the tray.

Furthermore, when packaging trays having a large length-to-width ratio,the amount of time the hot member touches each part of the flange of thetray can be made more uniform by operating the moving swivel shaftmechanism. For odd-shaped trays as well, sealing can be accomplished bymoving the swivel mechanism in both the X and Y directions.

Thus, since the apparatus described in this claim is provided with amoving swivel shaft mechanism, it can accommodate both odd-shaped traysand trays whose planar shape is rectangular or otherwise characterizedby a large length-to-width ratio better than an apparatus that merelyswivels the hot member around a fixed shaft.

A packaging apparatus in accordance with the tenth aspect of theinvention is an apparatus as recited in the ninth aspect which isfurther provided with a controller. The controller controls at least oneof the speed at which the hot member is swiveled by the swivel mechanismor the speed at which the swivel shaft is moved by the moving swivelshaft mechanism.

Since the packaging apparatus described in the ninth aspect isconfigured so that the hot member is moved along the flange by swivelingthe hot member, the amount of time the hot member touches each part ofthe flange will vary if a constant swivel speed is used on any tray thatis not circular in shape. This variance results in the occurrence ofpinholes and defective sealing (i.e., failure to achieve a seal) in theseal area. In order to reduce this variance, this claim calls forcontrolling the speed at which the swivel mechanism swivels the hotmember. Thus, the variance in the amount of time the hot member contactseach part of the tray can be reduced.

A packaging apparatus in accordance with the eleventh aspect of theinvention is an apparatus as recited in the eight aspect, wherein aplurality of said hot members are provided. The swivel mechanism has atleast two swivel shafts disposed in different planar positions. Theswivel mechanism moves the plurality of hot members by swiveling atleast one of the hot members about a first swivel shaft and swiveling atleast one of the hot members about a second swivel shaft.

With this apparatus, the swivel mechanism is provided with multipleswivel shafts; a hot member swivels about a first swivel shaft while ahot member also swivels about a second swivel shaft. Since the positionsof the first and second swivel shafts are planarly separated, the areaover which the hot members can be moved is the total of the swivel areasof both swivel shafts. Therefore, even if the tray has a largelength-to-width ratio, the hot members can be moved so that entireflange is accommodated by separating the two swivel shafts in thelengthwise direction of the rectangle. Furthermore, when packaging trayshaving a large length-to-width ratio, the amount of time hot memberstouch each part of the flange can be made more uniform.

Thus, since the swivel mechanism of the apparatus described in claim 11is provided with multiple swivel shafts and swivels a hot member aroundeach swivel shaft, it can accommodate trays whose planar shape isrectangular or otherwise characterized by a large length-to-width ratiobetter than an apparatus that merely swivels a hot member around asingle fixed swivel shaft.

It is also feasible to control the apparatus so that it uses only one ofthe multiple swivel shafts and the hot member that swivels around thatswivel shaft to conduct thermal welding on trays whose planar shape iscircular (or otherwise has a length-to-width ratio close to 1).

A packaging apparatus in accordance with the twelfth aspect of theinvention is an apparatus as recited in the eleventh aspect, which isfurther provided with a moving swivel shaft mechanism. The moving swivelshaft mechanism planarly moves at least one of swivel shafts.

With this apparatus, in addition to providing the swivel mechanism withmultiple swivel shafts, the apparatus is configured so that the movingswivel shaft mechanism can move the swivel shafts planarly.Consequently, the apparatus can accommodate trays having even largerlength-to-width ratios (or large rectangular trays). Furthermore, theamount of time the rollers touch each part of the flange can be mademore uniform by precisely controlling the movement of the swivel shafts.

A packaging apparatus in accordance with the thirteenth aspect of theinvention is an apparatus as recited in the twelfth aspect, which isfurther provided with a controller. The controller controls at least oneof the speed at which the hot member is swiveled by the swivel mechanismor the speed at which the swivel shaft is moved by the moving swivelshaft mechanism.

A packaging apparatus in accordance with the fourteenth aspect of theinvention is an apparatus as recited in the seventh aspect, wherein, themoving means moves the tray against the hot member.

A packaging apparatus in accordance with the fifteenth aspect of theinvention is an apparatus as recited in any one of the seventh throughfourteenth aspects, which is further provided with a film feeding means,a lift mechanism, and a hot member moving mechanism. The film feedingmeans feeds the film between the tray and the hot member. The liftmechanism lifts the tray and presses the flange of the tray against thefilm. The hot member moving mechanism moves the hot member and pressesit against the film at a portion of the flange of the tray, which hasbeen lifted by said lift mechanism.

With this apparatus, when a food product or other article is placed in atray is lifted by the lift mechanism, the film has been fed between thetray and the hot member presses against the flange of the tray. When thehot member moving mechanism moves the hot member, the hot member ispressed against the film on a portion of the flange. Then, when the hotmember and the tray are moved relative to each other by the movingmeans, the film is thermally welded to each portion of the flange.

A packaging apparatus in accordance with the sixteenth aspect of theinvention is an apparatus as recited in any one of the seventh throughfifteenth aspects, wherein a plurality of said hot members are provided.Hot members are so arranged that each hot member can touch a differentportion of the flange of the tray.

Since multiple hot members are provided, the amount by which each hotmember must be moved along the flange of the tray can be reduced incomparison with amount of movement required when only one hot member isprovided. That is, when only one hot member is provided, the hot membermust be moved at least one full revolution around the flange of the trayin order to weld the film to the entire flange of the tray. However,since this apparatus is provided with multiple hot members, the film canbe welded to the entire flange of the tray without moving each hotmember a full revolution around the flange.

Thus, the time required for the hot member moving means to move the hotmembers can be reduced and the efficiency of the packaging process canbe improved.

A packaging apparatus in accordance with the seventeenth aspect of theinvention is an apparatus as recited in any one of the seventh throughsixteenth aspects, which is further provided with a controller. Thecontroller controls the moving means to move at least one of the tray orthe hot member so that the film is thermally cut at the outside of thethermally welded portion while being thermally welded to the tray.

With this apparatus, the hot member that thermally welds the film to thetray is used to thermally cut the outer portion of the thermally weldedfilm. The film covers the tray and remains continuously connected to thefilm feeding means after the film is thermally cut. Therefore, the filmfeeding means can feed the film more smoothly and the film can be takenup more smoothly after cutting if a take-up means is provided whichtakes up the film that remains after the film is thermally cut.

Furthermore, the hot member can thermally cut the film more reliably ifa tensile force is applied to the film.

A packaging apparatus in accordance with the eighteenth aspect of theinvention is an apparatus as recited in any one of the seventh throughseventeenth aspects, wherein, the hot member is a heat-emitting rollerand rolls on the flange of the tray while the tray and the hot memberare moving relative to each other.

With this apparatus, the hot member (heat-emitting roller) rolls on theflange of the tray. That is, the hot member rotates as it moves over theflange. Therefore, the frictional resistance between the hot memberand-the film on the flange and the film is less likely to tear ordevelop tiny holes.

Also, it is preferable for the face of the hot member that contacts thefilm to be made of a resilient material (such as resin or syntheticrubber) so that firm contact can be maintained between the film and theflange even when small irregularities exist on the surface of the flangeof the tray.

A packaging apparatus in accordance with the nineteenth aspect of theinvention is an apparatus as recited in any one of the seventh througheighteenth aspects, wherein, the part of the hot member that touches theperiphery of the opening in the tray is made of an elastomer containingsilicon or fluoro rubber.

It is preferable for the face of the hot member that contacts the filmto be made of a resilient elastic material so that firm contact can bemaintained between the film and the tray even when small irregularitiesexist on the surface of the tray.

Therefore, with the apparatus described in claim 19, the part of the hotmember that touches the flange of the tray is made of an elastomercontaining silicon or fluoro rubber. The use of such an elastomer canalso make it more difficult for the hot member to damage the surface ofthe tray as it rolls on the tray. Furthermore, an elastomer containingsilicon or fluoro rubber is highly durable and therefore lesssusceptible to heat deterioration. Such elastomers also provide goodheat conduction and improve efficiency, and they reduce damage to thefilm because of their superior surface release property.

Also, since the part of the hot member that touches the flange of thetray is made of an elastomer containing silicon or fluoro rubber,friction between a roller and the film to be necessary for rotation ofthe roller is improved if the hot member is the roller.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of the packaging apparatus in the firstembodiment.

FIG. 2 is one state of the packaging apparatus in the first embodiment.

FIG. 3 is one state of the packaging apparatus in the first embodiment.

FIG. 4 is a plan view showing the arrangement of the tray and film inthe first embodiment.

FIG. 5 is a rotational motion of rollers in the first embodiment.

FIG. 6 is an enlarged view of the flange area when a roller contacts thetray in the first embodiment.

FIG. 7 is an enlarged view of the flange area when the film is thermallywelded to the tray in the first embodiment.

FIG. 8 illustrates a plan view of the tray shapes that the apparatus canaccommodate in the first embodiment.

FIG. 9 is an operation of the roller moving mechanism in the firstembodiment.

FIG. 10 is an operation of the roller moving mechanism in a variation onthe first embodiment.

FIG. 11 is a traverse cross section of the packaging apparatus in thesecond embodiment.

FIG. 12 is a longitudinal cross section packaging apparatus in thesecond embodiment.

FIG. 13 illustrates the operation of the packaging apparatus in thesecond embodiment.

FIG. 14 illustrates the operation of the packaging apparatus in thesecond embodiment.

FIG. 15 is a planar arrangement of the rollers in the second embodiment(as viewed across a XV—XV line shown in FIG. 12).

FIG. 16 is a planar path of the rollers resulting from swiveling in thesecond embodiment.

FIG. 17 is an enlarged view of the flange area when the rollers contactthe tray in the second embodiment.

FIG. 18 is an enlarged view of the flange area when the film isthermally welded to the tray in the second embodiment.

FIG. 19 illustrates how the roller path changes when the swivel shaftsare moved in the second embodiment.

FIG. 20 illustrates the operation of the rollers in the thirdembodiment.

FIG. 21 illustrates the operation of the rollers in the thirdembodiment.

FIG. 22 illustrates the operation of the rollers in the thirdembodiment.

FIG. 23 illustrates the operation of the rollers in the thirdembodiment.

FIG. 24 illustrates the operation of the rollers in the thirdembodiment.

FIG. 25 is a plan view of the roller arrangement in the second and thirdembodiment.

FIG. 26 is a schematic view of the packaging apparatus in the fourthembodiment.

FIG. 27 is one state of the packaging apparatus in the fourthembodiment.

FIG. 28 is a plan view showing the arrangement of the tray and film inthe fourth embodiment.

FIG. 29 is a rotational motion of tray in the fourth embodiment.

MODES FOR CARRYING OUT THE INVENTION First Embodiment

<Summary of the Apparatus>

First embodiment of a packaging apparatus in accordance with the presentinvention is shown in FIG. 1. The packaging apparatus 1 shown in thefigure is a so-called top-seal type packaging apparatus wherein theopening o on the upper portion of a tray T containing meat, fish, orother perishable food product is covered with a film Fm (see FIG. 6) andsealed by thermally welding film Fm to flange f, which is disposedaround the periphery of opening o in tray T.

<Constitution of the Apparatus>

Packaging apparatus 1 comprises chiefly the following components: aframe 1 a; a holding member 2, which holds tray T; four rollers 3positioned above holding member 2; a film feeding mechanism 5, whichfeeds film Fm between holding member 2 and rollers 3; a lift mechanism6, which raises and lowers holding member 2; a roller moving mechanism7, which moves rollers 3 chiefly up and down; a roller swivel mechanism8, which swivels rollers 3; and a controller (not shown), which controlsthe mechanisms.

<Detailed Descriptions of the Components>

(Holding Member)

Holding member 2 holds tray T on its upper surface and is raised andlowered by lift mechanism 6. Tray T may be placed on holding member 2either manually by an operator or automatically by a separate transportapparatus.

(Rollers)

Each roller 3 comprises a cylindrical member that is axially supportedby roller support 71 of roller moving mechanism 7 (discussed later) sothat the roller can rotate freely. The surface of roller 3 is providedwith a layer that is softer than other parts of the roller in order toreduce the frictional resistance between the roller and film Fm. Moreparticularly, the surface of roller 3 is made of a resilient material,such as resin or synthetic rubber, so that firm contact can bemaintained between film Fm and flange f even when small irregularitiesexist on the surface of flange f of tray T. Also, since friction betweenroller 3 and film Fm is improved, roller 3 rolls surely and film Fm issealed without occurrence of pinholes and other detective things. Asshown in FIG. 4, four rollers 3 are arranged radially with respect toshaft 81 of roller swivel mechanism 8 (discussed later). As shown inFIG. 1, rollers 3 are supported by roller supports 71 in such a mannerthat, when viewed from the side, they form an angle with respect to thehorizontal plane containing the upper face of tray T. The angle is setso that the end of each roller 3 that is closer to shaft 81 is higherthan the other end.

Inside each roller 3 is a heating element (not shown) for heating theroller 3. Appropriate specifications for the heating element areselected based on the materials from which the tray T and film Fm aremade and the necessity of supplying energy that can quickly replenishthe heat lost during the sealing operation.

(Film Feeding Mechanism)

Film feeding mechanism 5 delivers an amount of film Fm that isappropriate for the size of tray T to the space between lowered holdingmember 2 and rollers 3. Film feeding mechanism 5 comprises a deliverysection 51 which holds the supply of film Fm, a transport section whichtransports film Fm and is capable of clamping film Fm, and a take-upsection 53 which takes up the film Fm remaining after a portion has beencut away to package tray T. Delivery section 51, the transport section,and take-up section 53 are each supported by frame 1 a. The transportsection comprises: transport rollers 52 a, 52 b disposed on oppositesides of the space between holding member 2 and rollers 3; presserrollers 52 c, 52 d that press against the transport rollers; two beltsB1 that traverse transport rollers 52 a, 52 b; and two belts B2 thattraverse presser rollers 52 c, 52 d. With this particular film feedingmechanism 5, the film Fm held by delivery section 51 is transported bybelts B1 traversing transport rollers 52 a, 52 b and the two belts B2traversing presser rollers 52 c, 52 d and connects with take-up section53. Transport rollers 52 a, 52 b and take-up section 53 are operatedusing a motor or other driving means (not shown).

The controller can instruct the transport section to adjust the amountof film it carries in order to accommodate the size of tray T. The dataused to change the feed amount can be provided to the controller bymanually entering the size of tray T in advance or by using a measuringdevice to detect the size tray T.

The two belts B1 traversing transport rollers 52 a, 52 b and the twobelts B2 traversing presser rollers 52 c, 52 d can move freely in adirection roughly perpendicular to the direction in which film Fm is fed(the film moves from left to right in FIG. 1). When lift mechanism 6(discussed later) raises tray T, these belts apply tension to film Fm,making it possible to achieve a smooth film surface with no wrinklesover opening o in tray T.

Also, it is feasible to expand the width of film Fm by applying traversetension to film Fm. Thus a variety of tray sizes can be accommodated.

Also, reliability of cutting film Fm is improved if these belts applytension to film Fm after sealing.

Furthermore, by changing the amount of film Fm that the transport systemcarries between transport rollers 52 a, 52 b, a variety of tray sizescan be accommodated with a single size of film.

Belts B1, which transport film Fm, are made of a material that gripsonto film Fm and are structured so that the film can be sandwichedbetween belts B1 and the belts B2 traversing presser roller 52 c, 52 d.

(Lift Mechanism)

Lift mechanism 6 is a mechanism for lifting tray T against film Fm andcomprises: a drive motor 61; stationary section 62, which is affixed toframe 1 a; and moving section 63, which moves up and down with respectto stationary section 62. Holding member 2 is affixed to the upper faceof moving section 63. Thus, a tray T placed on holding member 2 israised and lowered according to the movement of moving section 63.

Drive motor 61 is a servomotor or a stepper motor, and its speed iscontrolled electronically by the controller. Since the movement ofmoving section 63 is controlled electronically, this embodiment allowsthe speed curve, stroke, and other aspects of the movement to be setrelatively easily, thus making it possible to raise and lower tray Tunder the conditions best suited to the size of tray T and the articlebeing packaged. Additionally, mechanisms and control methods other thanthe electronic control described above can also be used to move movingsection 63. Such mechanisms and control methods include mechanicalcontrol using cams and crank mechanisms and pneumatic control using aircylinders and the like.

(Roller Moving Mechanism)

Roller moving mechanism 7 is a mechanism for changing the verticalposition of rollers 3 and, as shown in FIGS. 1 and 9, comprises: rollersupports 71, which axially support rollers 3; link mechanism 72; presserplate 73; lever mechanism 74, which applies a force to the upper side ofpresser plate 73; and motor 75, which operates lever mechanism 74.

Roller supports 71 axially support rollers 3 in such a manner thatrollers 3 are angled as shown in FIG. 1 when viewed from the side. Oneend of link mechanism 72 supports roller support 71 with a pin and theother end is pressed downward by presser plate 73. When the other end oflink mechanism 72 is pressed down by presser plate 73, the one end israised as shown on the right side of FIG. 9. As a result, roller support71 and roller 3 are also brought to a raised position. Meanwhile, whenpresser plate 73 no longer applies a force to link mechanism 72, theopposite end of link mechanism 72 moves down due to the weight of rollersupports 71 and rollers 3 (see left side of FIG. 9).

Presser plate 73 is a disk shaped member that can move freely up anddown along shaft 81 of roller swivel mechanism 8 (discussed later). Theforce that moves presser plate 73 downward is provided from above bylever mechanism 74, which is driven by motor 75. The outer edge ofpresser plate 73 rests on the other end of link mechanism 72 (see FIG.9).

(Roller Swivel Mechanism)

Roller swivel mechanism 8 swivels rollers 3, as well as the rollersupports 71 and link mechanisms 72 that support them, through aprescribed angle when the package is being sealed and comprises shaft 81and motor 82, which rotates shaft 81. The lower end of shaft 81 is fixedto base 79, which supports link mechanism 72, and the upper end of shaft81 is connected to motor 82 via a timing belt and pulley (not shown).

When motor 82 responds to instructions from the controller and rotatesshaft 81 over a prescribed angle, rollers 3 swivel about shaft 81 overthe prescribed angle (see FIG. 5).

<Control Operations of the Apparatus>

When a tray T is loaded onto holding member 2 as shown in FIG. 1, thecontroller first calculates the amount of film Fm to be fed by filmfeeding mechanism 5 based on the size of tray T that was detected by ameasuring device or provided via manual input.

When the film feeding mechanism 5 has fed the calculated amount of filmFm, the transport section moves the two belts B1 that traverse transportrollers 52 a, 52 b and the two belts B2 that traverse presser rollers 52c, 52 d in a direction perpendicular to the transport direction(horizontal direction in FIG. 4). This movement of the belts stretchesfilm Fm in the traverse direction (vertical direction in FIG. 4), thustensioning film Fm in the traverse direction.

Lift mechanism 6 then lifts moving section 63 by the amount calculatedby the controller based on the size of tray T; tray T pushes film Fmupward and stops (see FIG. 2). The upward pressure of tray T tensionsfilm Fm in the transport direction.

Next the controller controls motor 75 so as to release the downwardforce lever mechanism 74 applies to presser plate 73, thus releasinglink mechanism 72. As a result, rollers 3 move into contact with tray Tdue to their own weight (see FIG. 3). Since rollers 3 are independent ofone another, each roller 3 contacts tray T with roughly the samepressure.

While simultaneously controlling motor 75 so that rollers 3 contact trayT, the controller instructs motor 82 to rotate shaft 81 through aprescribed angle. Since four rollers 3 are provided at an even spacingwith respect to the rotational direction (see FIG. 4), a prescribedangle of 90° would be sufficient for rollers 3 to seal the entireperiphery of tray T. However, in this embodiment, a slightly largerangle of 100° is used. When shaft 81 turns and rollers 3 begin to rotate(see FIG. 5), rollers 3 follow along the periphery (flange f) of tray Tand thermally weld film Fm to tray T, thus forming a seal. Here, rollers3 roll on flange f as they move.

FIG. 6 shows an enlarged view of the contact area between rollers 3 andtray T when the former move along the periphery of the latter. Theopening o in tray T is covered by film Fm, which is tensioned in boththe longitudinal and traverse directions, and film Fm is pressed againstflange f of tray T. Rollers 3 touch diagonally against the portion wherefilm Fm contacts flange f and apply both heat and pressure. This heatand pressure causes film Fm and flange f to thermally fuse together. Atthe same time, film Fm melts and is cut away at the edge portion (whichis, in this case, the apex of flange f where rollers 3 are touching) oftray T because the heat and pressure are concentrated on film Fm at theedge portion of tray T (see FIG. 7).

After rollers 3 have finished sealing film Fm to tray T, rollers 3 areraised and lift mechanism 6 lowers tray T. Then the sealed tray T isremoved from holding member 2 and the next cycle begins. When the nextcycle begins, film Fm, of which a portion has been thermally cut away inthe process of sealing tray T, is taken up by driving take-up section53. The width Fh of film Fm is set to be wider than the width Th of trayT (see FIG. 4); the continuity of film Fm is not severed as a result ofsealing tray T and trouble wherein it becomes impossible for take-upsection 53 to take up the film does not occur.

<Features of the Apparatus>

(1)

With this apparatus 1, each roller 3 contacts tray T independently andis made to roll while touching the upper surface of flange f of tray T.Therefore, unless it has an unusual shape, tray T can be packaged andsealed regardless of its shape or size. FIG. 8(b) provides a plan viewof the area in which apparatus 1 can execute the sealing operation; thearea is indicated as shaded area A (doughnut shaped area). Thus, theapparatus is not limited to the size and shape of tray T shown in FIG.8(a) but rather can seal any of the trays shown in FIG. 8(b)—namely, thelarge tray T2 indicated with a dotted line, the octagonal tray T3indicated with a single-dotted chain line, and the rectangular tray T4indicated with a double-dotted chain line—or any other shape and size oftray T that can fit with in area A.

Therefore, even in industries requiring a variety of different trays,apparatus 1 can provide efficient sealing without tools and othercomponents having to be changed. It also promotes the conservation ofresources by reducing the amount of film used and improves the safety offood products by providing a completely sealed package.

(2)

With this apparatus 1, rollers 3 contact only the portion of film Fmthat is on flange f and do not touch the portion of film Fm coveringopening o in tray T (see FIGS. 6 and 7) because rollers 3 are applied toflange f at an angle (slanted with respect to a horizontal plane). As aresult, the portion of film Fm covering opening o is less likely to meltor develop tiny holes.

(3)

With this apparatus, the pressure applied to flange f of tray T duringthermal welding can be adjusted by changing the slant angle of rollers3. The scaling time can also be adjusted by controlling the rotation ofmotor 82 so as to change the speed and speed curve of shaft 81. Bycombining temperature control of the heating elements that heat rollers3 with the ability to adjust the pressure and sealing time, sealingconditions that are well matched to tray T and film Fm can beestablished.

(4)

With this apparatus 1, tension is applied to film Fm in the traversedirection by moving the two belts B1 traversing transport rollers 52 a,52 b and the two belts B2 traversing presser rollers 52 c, 52 d andtension is applied to film Fm in the transport direction by lifting trayT. Since film Fm is tensioned when it is sealed to tray T, the problemof wrinkles existing in film Fm after sealing tray T is almosteliminated.

Also, since the sealing is conducted while film Fm is under tension, thethermal cutting of the outer portion of the thermally welded film Fm ismore easily accomplished. As shown in FIG. 7, rollers 3 thermally cutfilm Fm in a reliable manner.

(5)

With this apparatus 1, it is easy to recycle the trays because thetop-seal method adopted uses thermal welding instead of an adhesive.

A Variation on the First Embodiment

(A)

While the first embodiment uses a roller moving mechanism 7 like the oneshown in FIG. 9 to move rollers 3 chiefly downward with respect to trayT in order to establish contact, it is also acceptable to use a rollermoving mechanism 107 like the one shown in FIG. 10, which moves rollers3 chiefly horizontally with respect to tray T in order to establishcontact.

The apparatus shown in FIG. 10 is provided with link mechanism 172instead of link mechanism 72 of roller moving mechanism 7 and withrollers 103 instead of rollers 3. When presser plate 73 is pusheddownward, rollers 103 move horizontally away from shaft 81, as shown onthe right side of FIG. 10. When the force on presser plate 73 isreleased, rollers 103 move roughly horizontally toward shaft 81, asshown on the left side of FIG. 10.

Since rollers 103 approach tray T from the side, the distance over whichthey move is longer and the time required for the packaging operation islonger. However, the first embodiment enables larger trays to bepackaged than can be handled by roller moving mechanism 7 of the firstembodiment (FIG. 9).

In other words, with roller mechanism 7 (FIG. 9), rollers 3 must be longenough to accommodate the entire planar area defined by the maximum andminimum size of tray T used because rollers 3 move chiefly up and down,but the stroke of the movement that establishes contact with tray T issmaller. Also, when the slant angle of rollers 3 is increased, it issometimes necessary to change the stroke depending on the size of trayT.

Meanwhile, with roller moving mechanism 107 (FIG. 10), rollers 103 donot need to be particularly long even when tray T is large becauserollers 103 move chiefly horizontally. Also, the angle of rollers 103with respect to tray T can be set relatively freely. However, themovement stroke must be large enough to accommodate the maximum andminimum size of tray T. Furthermore, a separate mechanism that forcesrollers 3 inward is needed because sufficient sealing pressure cannot beobtained by simply using the weight of rollers 103.

(B)

In the first embodiment, rollers 3 are heated by a heating meansdisposed within rollers 3. However, it is also possible to use aconfiguration wherein the heating means is positioned separately fromrollers 3 and heats rollers 3 using microwaves or ultrasound.

Although, here, a configuration wherein rollers 3 roll on flange f oftray T is used to reduce the occurrence of wrinkling in film Fm and thedevelopment of holes in the portion of film Fm covering opening o duringthermal welding, it is not imperative that a rolling member be used onflange f. For example, a heated member with low frictional resistancemight be configured to slide as it moves along flange f. In such a case,in order to reduce resistance to the motion, it is desirable to apply afriction reducing treatment to at least that portion of the member whichcontacts the portion of film Fm resting on flange f.

(C)

In the first embodiment, the surface of rollers 3 is provided with alayer of material softer than the rest of the roller for the purpose ofincreasing the frictional resistance with respect to film Fm for surerotation of the roller 3. However, it is also possible to treat thesurface of rollers 3 so that the resistance reduces and change thesealing conditions.

(D)

In the first embodiment, moving section 63 of lift mechanism 6 is raisedso that tray T pushes upward against film Fm, thus generating tension infilm Fm. Depending on the strength of film Fm and the magnitude of thetension, there is the risk that film Fm will be damaged or that tray Twill be unnecessarily deformed. In order to reduce this risk, thedevelopment of excessive tension in film Fm when moving section 63 oflift mechanism 6 rises can be prevented by changing the positions oftransport rollers 52 a, 52 b and/or the degree to which presser rollers52 c, 52 d hold on to film Fm and synchronizing these changes withtiming at which film Fm comes into contact with tray T.

In the first embodiment, the width Fh of film Fm is wider than the widthTh of tray T (see FIG. 4). However, it is acceptable for the width Fh offilm Fm to be smaller than the width Th of tray T if the width Fhexceeds the width Th of tray T when traverse tension is applied to filmFm. Thus the continuity of film Fm would not be severed as a result ofsealing tray T and trouble wherein it becomes impossible for take-upsection 53 to take up the film would not occur.

Second Embodiment

<Summary of the Apparatus>

Second embodiment of a top-seal packaging apparatus in accordance withthe present invention is shown in FIGS. 11 and 12. The packagingapparatus 201 shown in the figures is an apparatus wherein the opening oin the upper portion of a tray T containing meat, fish, or otherperishable food product or a side dish or other processed food productis covered with a stretch film Fm (see FIG. 17) and sealed by thermallywelding stretch film Fm to a flange (periphery of the opening) f, whichis disposed around the periphery of opening o in tray T.

<Constitution of the Apparatus>

Packaging apparatus 201 comprises the following components: a frame 201a; a tray-holding mechanism 202, which holds tray T; four rollers 203positioned above tray-holding mechanism 202; a film transport mechanism205, which feeds stretch film Fm between tray-holding mechanism 202 androllers 203; a lift mechanism 206, which raises and lowers tray-holdingmechanism 202; a roller ascent-descent mechanism 207, which movesrollers 203 chiefly up and down; a roller swivel mechanism 208 with twoswivel shafts, which swivels rollers 203 around the swivel shafts 281 a,281 b; a stretch mechanism 209, which stretches stretch film Fm in thespace between tray-holding mechanism 202 and rollers 203; and acontroller (not shown), which controls each of the mechanisms.

<Detailed Descriptions of the Components>

(Tray-holding mechanism)

Tray-holding mechanism 202 holds tray T on its upper surface and israised and lowered by lift mechanism 206. As shown in FIG. 12, thetray-holding mechanism 202 can be drawn out to the position indicatedwith a double-dotted chain line or pushed in to the position indicatedwith a solid line by a slide mechanism. This horizontal movement isaccomplished manually or by a drive means (not shown). The slidemechanism is supported by pins and can hand the tray-holding mechanism202 to lift mechanism 206.

Tray T may be placed on tray-holding mechanism 202 either manually by anoperator or automatically by a separate transport apparatus.

(Rollers)

Each roller 203 comprises a cylindrical member that is axially supportedby roller support 271 of roller ascent-descent mechanism 207 (discussedlater) so that the roller can rotate freely. The surface of roller 203is provided with a layer that is softer than other parts of the roller.More particularly, the surface of roller 203 is made of an elastomer, sothat firm contact can be maintained between stretch film Fm and flange feven when small irregularities exist on the surface of flange f of trayT.

Here, the elastomer used is one that contains heat resistant silicon orfluoro rubber. Using this kind of elastomer reduces the chance thatrollers 203 will damage the surface of tray T as they roll on the trayand reduces susceptibility to heat deterioration because the elastomeris highly heat resistant. Also, rollers 203 rolls surely and stretchfilm Fm is sealed without occurrence of pinholes and other defectivethings because the friction between roller 203 and film Fm is improvedby using the elastomer. Such elastomers also provide good heatconduction and improve efficiency, and they reduce damage to the stretchfilm because they improve surface release properties.

As shown in FIG. 15, two rollers 203 are provided for each of swivelshafts 281 a, 281 b of roller swivel mechanism 208 (discussed later).FIG. 15 shows the arrangement of rollers 203 when viewed fromunderneath. Thus, from a planar perspective, rollers 203 are arranged asshown in FIG. 15 and are mounted to swivel shafts 281 a, 281 b at anangle of roughly 110°. FIG. 15 is a simplified figure and a planararrangement of rollers 203.

As shown in FIGS. 11 and 12, rollers 203 are supported by rollersupports 271 in such a manner that, when viewed from the side, they forman angle with respect to the horizontal plane containing the upper faceof tray T. The angle is set so that the end of each roller 203 that iscloser to swivel shafts 281 a, 281 b is higher than the other end.

Inside each roller 203 is a heating element (not shown) for heating theroller 203. Appropriate specifications for the heating element areselected based on the materials from which the tray T and stretch filmFm are made and the necessity of supplying energy that can quicklyreplenish the heat lost during the sealing operation.

(Film Transport Mechanism)

Film transport mechanism 205 delivers an amount of stretch film Fm thatis appropriate for the size of tray T to the space between loweredtray-holding mechanism 202 and rollers 203. As shown in FIG. 11, filmtransport mechanism 205 comprises a film delivery section 251, a filmtransport section 252, and a film take-up section 253. Film deliverysection 251, film transport section 252, and film talk-up section 253are each supported by frame 201 a.

The film delivery section 251 serves as the supply source of stretchfilm Fm and comprises members that rotatably support film roll R ofstretch film Fm. Stretch film delivery section 251 has a core supportmember 251 a, which can move up and down, and a support roller 251 b,which supports film roll R at an angle from underneath. Film roll R issupported (see FIG. 11) by core support member 251 a, support roller 251b, and delivery roller 252 a of film transport section 252 (discussedlater).

The film take-up section 253 has a take-up shaft 253 a and is providedto take up the stretch film Fm that remains after a portion has been cutaway to package (top-seal) tray T. Take-up shaft 253 a is rotated bybelt 253 b, which is connected to motor 252 c (discussed later).

The film transport section 252 is provided with: delivery roller 252 a;motor 252 c, which rotates delivery roller 252 a via belt 252 b; andfilm support roller 252 d. The stretch film Fm taken from film roll R isfed toward film take-up section 253 by the rotation of delivery roller252 a. Film delivery roller 252 a and support roller 251 b are disposedsymmetrically with respect to core support member 251 a. The distancebetween delivery roller 252 a and support roller 251 b is set to besmaller than the diameter of the core of film roll R. These rollers 252a, 251 b prevent film roll R from dropping down. Film support roller 252d is positioned close to film take-up roller 253 and its height is setso that its upper surface is aligned with the lower surface of deliveryroller 252 a (see FIG. 11).

(Stretch Mechanism)

Stretch mechanism 209 grips both sides of stretch film Fm, which runsfrom film delivery section 251 to film take-up section 253, in thehorizontal section between delivery roller 252 a and film support roller252 d and stretches stretch film Fm in the traverse direction(horizontal direction in FIG. 12). Stretch mechanism 209 is providedwith a pair of film grippers 291 a, 291 b extending in the filmtransport direction and a stretch drive section (not shown), which movesthe grippers perpendicularly (horizontal direction in FIG. 12) to thefilm transport direction.

Film grippers 291 a, 291 b comprise a mechanism that grips stretch filmFm by sandwiching it from the top and bottom and are turned ON and OFFusing a solenoid. Slippage between film grippers 291 a, 291 b andstretch film Fm is prevented by mounting a rubber (or resin) pad havinga large coefficient of friction on the part that contacts the upper sideof stretch film Fm.

The stretch drive section comprises a guide rail, a motor, a sprocket, achain, etc, and moves film grippers 291 a, 291 b to the left and right(when viewed as shown in FIG. 12) in response to instructions from thecontroller.

(Lift Mechanism)

Lift mechanism 206 is a mechanism for lifting tray-holding mechanism202, while the same holds a tray T, against stretch film Fm, as shown inFIG. 13. Lift mechanism 206 comprises: a drive motor 261; large gear262, which is axially supported by frame 201 a; link member 263; lever264, one end of which is axially supported by frame 201 a at supportpoint 264 a; disk member 265, which is rotatably mounted to the end oflever 264; etc.

When drive motor 261 operates, a gear affixed to the motor shaft rotateslarge gear 262 and link member 263 causes lever 264 to pivot aboutsupport point 264 a. As a result, tray-holding mechanism 202 moves up ordown (see FIGS. 12 and 13) because its underside is supported by diskmember 265. Also, tray support mechanism 202 is guided by vertical guiderails 269 and moves in the vertical direction in response to theoperation of lift mechanism 206.

(Roller Ascent-descent Mechanism)

Roller ascent-descent mechanism 207 is a mechanism for changing thevertical position of rollers 203 and, as shown in FIG. 11, comprises:roller supports 271, which axially support rollers 203; link mechanism272; presser plate 273; lever mechanism 274, which applies a force tothe upper side of presser plate 273; and motor 275, which operates levermechanism 274.

Roller supports 271 axially support rollers 203 in such a manner thatrollers 203 are angled as shown in FIGS. 11 and 12 when viewed from theside. The rotational axis of each roller 203 is indicated in FIGS. 11and 12 by a single-dotted chain line passing through the roller 203. Oneend of link mechanism 272 supports roller support 271 with a pin and theother end is pressed downward by presser plate 273. When the other endof link mechanism 272 is pressed down by presser plate 273, the one endis raised as shown in FIGS. 11 and 12. As a result, roller support 271and roller 203 are also brought to a raised position. Meanwhile, whenpresser plate 273 no longer applies a force to link mechanism 272, theopposite end of link mechanism 272 moves down due to the weight ofroller support 271 and roller 203 (see FIGS. 12 and 14).

The force that moves presser plate 273 is provided from above by levermechanism 274, which is driven by motor 275. The outer edge of presserplate 273 rests on a rolling member axially supported on the other endof link mechanism 272 (see FIG. 19).

(Roller Swivel Mechanism)

Roller swivel mechanism 208 swivels rollers 203, as well as the rollersupports 271 and link mechanisms 272 that support them, through aprescribed angle when the package is being sealed. Roller swivelmechanism 208 comprises chiefly: a first swivel shaft 281 a; a secondswivel shaft 281 b; and a motor 282, which rotates both swivel shafts281 a, 281 b.

The lower end of first swivel shaft 281 a is fixed to a base 279, whichsupports two of link mechanisms 272, and the upper end is meshed withmain gear 283 via a gear. Main gear 283 is connected to motor 282 by apulley and a belt 284 and rotates when motor 282 operates.

The lower end of second swivel shaft 281 b is fixed to a separate base279 (a separate member from the base 279 to which first swivel shaft 281a is fixed), which supports the other two link mechanisms 272. The upperend of second swivel shaft 281 b is meshed with main gear 283 via a gear(see FIG. 15).

When motor 282 responds to instructions from the controller and rotatesswivel shafts 281 a, 281 b over a prescribed angle, each roller 203revolves through the prescribed angle about first swivel shaft 281 a orsecond swivel shaft 281 b (see FIG. 16). In FIG. 16, for clarity, therollers 203 linked to first swivel shaft 281 a are indicated as roller203 a and roller 203 b and the rollers 203 linked to second swivel shaft281 b are indicated as roller 203 c and roller 203 d. Also, in FIG. 16,the positions of rollers 203 before swiveling are indicated with solidlines and the positions of rollers 203 after swiveling are indicatedwith dotted lines.

<Control Operations of the Apparatus>

Once a tray T containing a food product or other article is loaded ontotray-holding mechanism 202, which has been drawn out to the positionindicated with a double-dotted chain line in FIG. 12, tray-holdingmechanism 202 is moved horizontally under rollers 203 by hand or using adriving means not shown.

After tray-holding mechanism 202 has moved underneath rollers 203,multiple holding members push against the sides of tray T and positiontray T, thus holding tray T so that tray T is prevented from moving outof place.

Additionally, when tray T is loaded onto tray-holding mechanism 202, acamera (not shown) detects the size of tray T and sends the size data tothe controller.

Based on the size of tray T, the controller identifies the type of trayT and calculates the amount of stretch film Fm to be fed by filmtransport mechanism 205.

When the film transport mechanism 205 has fed the calculated amount ofstretch film Fm, the controller operates stretch mechanism 209 tostretch stretch film Fm in the traverse direction (horizontal directionin FIG. 12). As a result, stretch film Fm is tensioned in the traversedirection and has no wrinkles.

Next the controller operates lift mechanism 206 and lifts tray-holdingmechanism 202, which is holding tray T. Tray T pushes stretch film Fmupward and stops (see FIG. 13).

Next the controller controls motor 275 so as to release the downwardforce lever mechanism 274 applies to presser plate 273, thus releasinglink mechanism 272. As a result, rollers 203 move down into contact withtray T due to their own weight (see FIG. 14). Since rollers 203 areindependent of one another, each roller 203 contacts tray T with roughlythe same pressure.

Next the controller instructs motor 282 to rotate swivel shafts 281through a prescribed angle. The prescribed angle is set so that theentire flange f of tray T will be sealed by one of rollers 203 a through203 d; in this embodiment, an angle of 110° is used (see FIG. 16).

When rollers 203 are swiveled about swivel shafts 281 a, 281 b and beginto roll over the stretch film Fm on tray T, rollers 203 thermally weldstretch film Fm to flange f of tray T.

FIG. 17 shows an enlarged view of the contact area between rollers 203and tray T when the former move along the periphery of the latter. Theopening o of tray T is covered by stretch film Fm, and stretch film Fmis pressed against flange f of tray T. Rollers 203 touch diagonallyagainst the portion where stretch film Fm contacts flange f and applyboth heat and pressure. This heat and pressure causes stretch film Fmand flange f to thermally fuse together. At the same time, stretch filmFm melts and is cut away at the edge portion (which is, in this case, aportion to the outside of the apex of flange f where rollers 203 aretouching) of tray T because the heat and pressure are concentrated onstretch film Fm at the edge portion of tray T (see FIG. 18). Thecontroller swivels rollers 203 at a speed that allows the stretch filmto be thermally cut along the outside of the portion bonded by thermalwelding while stretch film Fm is being thermally welded to flange f.

After rollers 203 have finished sealing stretch film Fm to tray T,rollers 203 are raised and tray T is lowered. Then the sealed tray T isremoved from drawn out tray-holding mechanism 202 and the next cyclebegins.

When the next cycle begins, stretch film Fm, of which a portion has beenthermally cut away in the process of sealing tray T, is wound ontotake-up shaft 253 a. At the same time, motor 252 c rotates film supportroller 252 d and delivery roller 252 a so that the stretch film Fm forthe next cycle is fed (supplied to the area below rollers 203)simultaneously with the taking up of the cut film.

The width of stretch film Fm is selected so that the width of the filmwill be exceed the width of tray T when the film is stretched by stretchmechanism 209. Thus, the continuity of stretch film Fm is not severed asa result of sealing tray T (i.e., cutting a hole in stretch film Fm) andtrouble wherein it becomes impossible for film take-up section 253 totake up the film does not occur.

<Features of the Packaging Apparatus>

(1)

With this apparatus 201, roller swivel mechanism 208 is provided withtwo swivel shafts 281 a, 281 b so that rollers 203 a, 203 b are swiveledabout first swivel shaft 281 a and rollers 203 c, 203 d are swiveledabout second swivel shaft 281 b (FIG. 16). Since the positions of firstand second swivel shafts 281 a, 281 b are planarly separated, themovement area over which rollers 203 can be moved is the total of theswivel areas of both swivel shafts 281 a, 281 b.

Looking at FIG. 16, the movement area for rollers 203 a through 203 d isthe total of swivel area A1 and swivel area A2, where swivel area A1 isthe area over which first swivel shaft 281 a moves rollers 203 a, 203 band swivel area A2 is the area over which second swivel shall 281 bmoves rollers 203 c, 203 d.

Therefore, even if the tray has a large length-to-width ratio, therollers 203 can be moved so that entire flange f is accommodated byaligning the lengthwise direction of the direction in which the twoswivel shafts 281 a, 281 b are separated.

Furthermore, when packaging trays having a large length-to-width ratio,the variance in the amount of time rollers 203 touch each part of flangef is reduced in comparison to when the rollers are swiveled by a singleswivel shaft.

(2)

With this apparatus 201, two rollers 203 a, 203 b are swiveled aboutfirst swivel shaft 281 a and two rollers 203 c, 203 d are swiveled aboutsecond swivel shaft 281 b. Therefore, the time required for packaging(thermal welding) is reduced in comparison to when only one roller iscoupled to each swivel shaft.

(3)

With this apparatus 201, rollers 203 contact only the portion of stretchfilm Fm that is on flange f and do not touch the portion of stretch filmFm covering opening o of tray T (see FIGS. 17 and 18) because rollers203 are applied to flange f at an angle (slanted with respect to ahorizontal plane). As a result, the portion of stretch film Fm coveringopening o is less likely to melt or develop tiny holes.

(4)

With this apparatus 201, the pressure applied to flange f of tray Tduring thermal welding can be adjusted by changing the slant angle ofrollers 203. The sealing time can also be adjusted by controlling therotation of motor 282 so as to change the speed and speed curve ofswivel shafts 281 a, 281 b. By combining temperature control of theheating elements that heat rollers 203 with the ability to adjust thepressure and sealing time, sealing conditions that are well matched totray T and stretch film Fm can be established.

(5)

With this apparatus 201, since the stretch film Fm is tensioned bystretch mechanism 209 when tray T is lifted, the problem of wrinklesexisting in stretch film Fm after stretch film Fm is sealed to tray T isalmost eliminated.

(6)

With this apparatus 201, tray T is lifted up while both sides of stretchfilm Fm are gripped by film grippers 291 a, 291 b of stretch mechanism209. Therefore, when the apparatus is in the state shown in FIG. 13 or14, tension develops in the portions of stretch film Fm between tray Tand each of the two film grippers 291 a, 291 b. The portions of stretchfilm Fm between tray T and delivery roller 252 a and between tray T andfilm support roller 252 d also develop tension. Since the portion ofstretch film Fm around the perimeter (outside) of tray T is tensionedwhen heat sealing is conducted, thermal cutting of the outer portion ofthe thermally welded stretch film Fm is more easily accomplished androllers 203 thermally cut stretch film Fm (see FIG. 18) in an reliablemanner.

A Variation on the Second Embodiment

In the second embodiment, the planar positions of both swivel shafts 281a, 281 b are fixed, but the range of applicable sizes and shapes of traycould be increased even further by making one or both shafts movable.

In this embodiment, swivel shafts 281 a, 281 b are replaced with swivelshafts 381 a, 381 b, which are planarly moveable in the film transportdirection (the vertical direction in FIG. 19), and rollers 203 areconnected to swivel shafts 381 a, 381 b. Swivel shafts 381 a, 381 b aremoved planarly by an electric powered ball screw mechanism and crankmechanism based on instructions from the controller.

With this configuration, a large-sized tray T that extends outsideswivel area A3 of rollers 203 a through 203 d when the distance betweenswivel shafts 381 a, 381 b is S1, as shown in FIG. 19(a), can besuccessfully heat sealed by moving swivel shafts 381 a, 381 b so thatthe distance between them increases to S2, as shown in FIG. 19(b), andthus expanding the swivel area of rollers 203 a through 203 d from A3 toA4. In FIG. 19, the positioning of rollers 203 before swiveling isindicated with solid lines and the positioning of rollers 203 afterswiveling is indicated with dotted lines.

By controlling the swivel speed and also executing precise control ofthe motion between swivel shafts 381 a, 381 b, using the controller, theamount of time rollers 203 are in contact with each portion of flange fof tray T can be brought closer to a fixed value (optimum value).

Third Embodiment

In the Second embodiment, the movement area of rollers 203 is expandedby providing roller swivel mechanism 208 with two swivel shafts 281 a,281 b. However, it is also possible to expand the movement area ofrollers 203 by planarly moving a single swivel shaft.

<Constitution>

This embodiment adopts a configuration wherein single swivel shaft 481is moved in the longitudinal direction of tray T (vertical direction inFIG. 20) using a moving mechanism (not shown). One roller 203 isconnected to swivel shaft 481 using a base member and a link mechanism.Thus, roller 203 swivels around swivel shaft 481 when swivel shaft 481rotates.

<Operation>

The first thing the controller does after it has lifted tray T upwardagainst stretch film Fm and touched roller 203 against tray T is rotateswivel shaft 481 180°.

Then roller 203 swivels, moving from the state shown in FIG. 20 to thestate shown in FIG. 21. The shaded area in FIG. 21 indicates the path ofroller 203. The stretch film is thermally welded to the portion of theflange of tray T located in this area during the stage of the sealingprocess illustrated in FIG. 21.

Next the controller moves swivel shaft 481 horizontally. As a result,roller 203 also moves horizontally from the state shown in FIG. 21 tothe state shown in FIG. 22. This movement results in the stretch filmbeing thermally welded to the middle portion of one of the long sides oftray T.

The controller then rotates swivel shaft 481 180°, causing roller 203 tomove from the state shown in FIG. 22 to the state shown in FIG. 23. Nextswivel shaft 481 is moved horizontally back to its original position(see FIG. 24) and roller 203 completes a path around the entire flangeof tray T. Thus, the stretch film is thermally welded so that theopening in tray T is sealed.

<Features>

In addition to a roller swivel mechanism 208 for swiveling roller 203,this embodiment of the packaging apparatus is provided with a movingmechanism that moves swivel shaft 481 planarly. When large rectangulartrays or trays with a large length-to-width ratio are packaged, roller203 is moved over the entire flange of the tray by moving swivel shaft481. Thus, the entire flange can be accommodated even when the tray isof a shape (or size) that roller 203 cannot follow using swivelingalone, that is, a tray that extends outside the path of roller 203(i.e., the movement area of roller 203) when swiveling alone is used.

Also, even in those situations where the path of roller 203 provided byswiveling alone accommodates the entire flange of the tray, the amountof time roller 203 touches each portion of the flange of the tray can bemade more uniform by moving roller 203 using a combination of swivelingand planar motion. The amount of time roller 203 touches each portion ofthe flange of the tray can be brought even closer to a fixed value bycontrolling the swivel speed and the planar motion speed.

When packaging trays whose planar shape is circular, the amount of timeroller 203 touches each portion of the flange of the tray can be madeuniform by controlling the apparatus so that swivel shaft 481 remainsplanarly immobile.

A Variation on the Second and Third Embodiments

(A)

In the second and third embodiments, rollers 203 are heated by a heatingmeans disposed within rollers 203. However, it is also possible to use aconfiguration wherein the heating means is positioned separately fromrollers 203 and heats rollers 203 using microwaves or ultrasound.

(B)

Although in the second and third embodiments, a configuration whereinrollers 203 roll on flange f of tray T is used to reduce the occurrenceof wrinkling in stretch film Fm and the development of holes in theportion of stretch film Fm covering opening o during thermal welding, itis not imperative that a rolling member be used on flange f. Forexample, a heated member with low frictional resistance might beconfigured to slide as it moves along flange f. In such a case, in orderto reduce resistance to the motion, it is desirable to apply a frictionreducing treatment to at least that portion of the member which contactsthe portion of stretch film Fm resting on flange f.

(C)

In the second and third embodiments, the surface of rollers 203 isprovided with a layer of material softer than the rest of the roller.Therefore, the frictional resistance with respect to stretch film Fm isincreased and rollers 203 roll surely. Adhesion of rollers 203 tostretch film Fm is also improved. However, it is also possible to treatthe surface of rollers 203 so that the resistance reduces and change thesealing conditions.

(D)

In the second embodiment, roller swivel mechanism 208 is provided withtwo swivel shafts 281 a, 281 b and each swivel shaft 281 a, 281 b hastwo rollers 203 connected thereto. However, as shown in FIG. 25, it isalso possible to provide the roller swivel mechanism with four swivelshafts 581 a, 581 b, 581 c, 581 d and connect one roller 203 to eachswivel shafts 581 a, 581 b, 581 c, 581 d. Such a configuration wouldpermit packaging with a similar processing time to that achieved withthe second embodiment.

Although second embodiment adopts a configuration wherein the fourswivel shafts 581 a, 581 b, 581 c, 581 d are meshed with the same maingear 283, it is also possible to provide each swivel shaft 581 a, 581 b,581 c, 581 d with its own rotationally driving motor (four motors) andcontrol the rotational speed of each swivel shaft 581 a, 581 b, 581 c,581 d. Such a configuration would allow the amount of time rollers 203touch each part of the flange of the tray to be made even more uniform.

Fourth Embodiment

While the first embodiment uses a roller swivel mechanism 8 to swivelrollers 3 against tray T as shown in FIG. 5, it is also acceptable tofix rollers 3 and rotate the tray against rollers 3.

In the fourth embodiment, a tray rotation mechanism 108 is replaced withthe roller swivel mechanism as shown in FIGS. 26 and 27. Therefore,rollers 3 do not swivel. But the roller moving mechanism 7 changes thevertical position of rollers 3.

Tray rotation mechanism 108 comprises shaft 181 and motor 182, whichrotates shaft 181. The upper end of shaft 181 fixed to a tray-holdingmechanism 102, which holds tray T. The lower end of shaft 181 isconnected to motor 182.

When the controller starts motor 182, the tray-holding mechanism 102rotates. The controller controls rotation of motor 182. Motor 182 fixedto a moving portion 63 of lift mechanism 6 (see FIGS. 26 and 27).

Tray-holding mechanism 102 holds tray T on its upper surface.Tray-holding mechanism 102 also holds the sides of tray T so that tray Tis prevented from moving out of place, especially rotating. Tray-holdingmechanism 102 has four side-holding members 102 a pushing against thesides of tray T and prevent from moving as shown in FIG. 26.

<Control Operations of the Apparatus>

When a tray T is loaded onto tray-holding mechanism 102 and is held byside-holding members 102 a as shown in FIG. 26, film feeding mechanism 5feeds film Fm. Then, the two belts B1 that traverse transport rollers 52a, 52 b and the two belts B2 that traverse presser rollers 52 c, 52 dare moved in a direction perpendicular to the transport direction(horizontal direction in FIG. 28). This movement of the belts stretchesfilm Fm in the traverse direction (vertical direction in FIG. 28), thustensioning film Fm in the traverse direction.

Lift mechanism 6 then lifts moving section 63 by the amount calculatedby the controller based on the size of tray T; tray T pushes film Fmupward and stops. The upward pressure of tray T tensions film Fm in thetransport direction.

Next the controller controls motor 75 so as to release the downwardforce lever mechanism 74 applies to presser plate 73, thus releasinglink mechanism 72. As a result, rollers 3 move into contact with tray Tdue to their own weight (see FIG. 27). Since rollers 3 are independentof one another, each roller 3 contacts tray T with roughly the samepressure.

While simultaneously controlling motor 75 so that rollers 3 contact trayT, the controller instructs motor 182 of tray rotation mechanism 108 torotate shaft 181 through a prescribed angle. Since four rollers 3 areprovided at an even spacing with respect to the rotational direction(see FIG. 28), a prescribed angle of 90° would be sufficient for rollers3 to seal the entire periphery of tray T. However, in this embodiment, aslightly larger angle of 100° is used. When shaft 181 turns and rollers3 begin to rotate (see FIG. 29), rollers 3 follow along the periphery(flange f) of tray T and thermally weld film Fm to tray T, thus forminga seal. Here, rollers 3 roll on flange f as they move on account ofrotation of tray T.

After rollers 3 have finished sealing film Fm to tray T, rollers 3 areraised and lift mechanism 6 lowers tray T. Then the sealed tray T isremoved from tray rotation mechanism 108 and the next cycle begins. Whenthe next cycle begins, film Fm, of which a portion has been thermallycut away in the process of sealing tray T, is taken up by drivingtake-up section 53. The width Fh of film Fm is set to be wider than thewidth Th of tray T (see FIG. 28); the continuity of film Fm is notsevered as a result of sealing tray T and trouble wherein it becomesimpossible for take-up section 53 to take up the film does not occur.

A Variation on the Fourth Embodiment

While the tray is rotated against rollers in the fourth embodiment androllers are swiveled against tray in the first embodiment, it is alsoacceptable to rotate the tray and swivel rollers simultaneously.

INDUSTRIAL APPLICABILITY

With this invention, since the hot member and the tray are movedrelative to each other, various shapes and sizes of tray can beaccommodated. Unlike conventional top-seal methods, it is not necessaryto prepare tools for each different type of tray and the efficiency ofpackaging operations can be improved.

Also, since the hot member is applied at an angle to the flange, the hotmember does not come in contact with a portion of the film covering theopening. Consequently, the portion of the film that covers the openingis less likely to melt or develop tiny holes.

What is claimed is:
 1. A packaging method comprising: putting an articleto be packaged on a tray having an opening defined by a flange lying ina first plane in its upper face; covering the opening in the tray with afilm substantially lying in the first plane; touching a face of at leastone heated hot member against the film on a portion of the tray near theopening where the film touches with the face of the heated hot memberlying in a second plane forming an angle with the first plane whentouching; and moving at least one of the heated hot member and the traywhile the heated hot member is touching against the film on the portionof the tray.
 2. A packaging method set forth in claim 1, wherein themoving of at least one of the heated hot member and the tray includesthe heated hot member moving along a periphery of the opening in thetray.
 3. A packaging method set forth in claim 1, wherein during thetouching of the face of the at least one heated hot member against thefilm and the moving of at least one of the heated hot member and thetray, the heated hot member not only thermally welds the film to aportion of the tray near the opening but also cuts an outer portion ofthe thermally welded film.
 4. A packaging method set forth in claim 1,wherein during the moving of at least one of the heated hot member andthe tray, the heated hot member rolls as it moves along a periphery ofthe opening in the tray.
 5. A packaging method set forth in claim 1,wherein during the moving of at least one of the heated hot member andthe tray, the face of the heated hot member is varied relative to thefirst plane.
 6. A packaging method comprising: a first step of puttingan article to be packaged on a tray having an opening in its upper face;a second step of covering the opening in the tray with a film; a thirdstep of touching, in a direction intersecting with a vertical direction,a heated hot member against the film on a portion of the tray near theopening where the film touches; and a fourth step of moving the heatedhot member while the heated hot member is touching against the film onthe portion of the tray, the heated hot member being moved along aperiphery of the opening in the tray by swiveling the heated hot memberabout a swivel shaft while planarly moving the swivel shaft.
 7. Apackaging method comprising: a first step of putting an article to bepackaged on a tray having an opening in its upper face; a second step ofcovering the opening in the tray with a film; a third step of touching,in a direction intersecting with a vertical direction, a plurality ofheated hot members against the film on a portion of a periphery of theopening in the tray near the opening where the film touches; and afourth step of moving the heated hot members while the heated hotmembers are touching against the film on the portion of the periphery ofthe opening in the tray, the heated hot members being moved along theperiphery of the opening in the tray by swiveling the plurality ofheated hot members about axes of at least two swivel shafts disposed indifferent planar positions.
 8. A packaging apparatus, in which a trayprovided with a flange and an opening surrounded by the flange on itsupper face and containing an article to be packaged, is covered with afilm over the opening and the film is welded to the flange, thepackaging apparatus comprising: a support member arranged to support thetray with a portion of the flange lying in a first plane thatsubstantially contains the film when welded to the flange; a hot memberhaving a face arranged and configured to touch against the film on aportion of the flange of the tray, the face being arranged to be lyingin a second plane that forms an angle with respect to the first planewhen touching; and moving means for moving at least one of the hotmember and the tray while the hot member is touching against the film onthe portion of the flange of the tray.
 9. A packaging apparatus setforth in claim 8, wherein the moving means moves the hot member againstthe tray.
 10. A packaging apparatus set forth in claim 8, wherein themoving means moves the tray against the hot member.
 11. A packagingapparatus set forth in claim 8, wherein the hot member is aheat-emitting roller and rolls on the flange of the tray while the trayand the hot member are moving relative to each other.
 12. A packagingapparatus set forth in claim 8, wherein the face of the hot member thattouches against the film on the portion of the flange of the tray ismade of an elastomer containing silicon or fluoro rubber.
 13. Apackaging apparatus, in which a tray provided with a flange and anopening surrounded by the flange on its upper face and containing anarticle to be packaged is covered with a film over the opening and thefilm is welded to the flange, the packaging apparatus comprising: a hotmember having a face that is capable of touching against the film on aportion of the flange of the tray, the face capable of touching the filmbeing at an angle with respect to a horizontal plane; and moving meansfor moving the hot member while the hot member is touching against thefilm on the portion of the flange of the tray, the moving meanscomprising: a swivel mechanism which swivels the hot member about aswivel shaft; and a moving swivel shaft mechanism which planarly movesthe swivel shaft of the swivel mechanism.
 14. A packaging apparatus setforth in claim 13, further comprising a controller that controls atleast one of a speed at which the hot member is swiveled by the swivelmechanism and a speed at which the swivel shaft is moved by the movingswivel shaft mechanism.
 15. A packaging apparatus, in which a trayprovided with a flange and an opening surrounded by the flange on itsupper face and containing an article to be packaged, is covered with afilm over the opening and the film is welded to the flange, thepackaging apparatus comprising: a plurality of hot members having facesthat are capable of touching against the film on a portion of the flangeof the tray, the faces capable of touching the film being at an anglewith respect to a horizontal plane; and moving means for moving the hotmembers while the hot members are touching against the film on theportion of the flange of the tray, the moving means having a swivelmechanism with at least two swivel shafts disposed in different planarpositions, the swivel mechanism moving the plurality of hot members byswiveling at least one of the hot members about a first swivel shaft andswiveling at least one of the hot members about a second swivel shaft.16. A packaging apparatus set forth in claim 15, wherein said movingmeans further has a moving swivel shaft mechanism which planarly movesat least one of the swivel shafts.
 17. A packaging apparatus set forthin claim 16, further comprising a controller that controls at least oneof a speed at which the hot members are swiveled by the swivel mechanismand a speed at which the swivel shaft is moved by the moving swivelshaft mechanism.
 18. A packaging apparatus, in which a tray providedwith a flange and an opening surrounded by the flange on its upper faceand containing an article to be packaged, is covered with a film overthe opening and the film is welded to the flange, the packagingapparatus comprising: a hot member having a face that is capable oftouching against the film on a portion of the flange of the tray, theface capable of touching the film being at an angle with respect to ahorizontal plane; and moving means for moving at least one of the hotmember and the tray while the hot member is touching against the film onthe portion of the flange of the tray; a film feeding means for feedingthe film between the tray and the hot member; a lift mechanism whichlifts the tray and presses the flange of the tray against the film; anda hot member moving mechanism which moves the hot member and presses itagainst the film at the portion of the flange of the tray, which hasbeen lifted by the lift mechanism.
 19. A packaging apparatus, in which atray provided with a flange and an opening surrounded by the flange onits upper face and containing an article to be packaged, is covered witha film over the opening and the film is welded to the flange, thepackaging apparatus comprising: a plurality of hot members having facesthat are capable of touching against the film on a portion of the flangeof the tray, the faces capable of touching the film being at an anglewith respect to a horizontal plane, the hot members being so arrangedthat each hot member can touch the film on a different portion of theflange of the tray; and moving means for moving at least one of the hotmembers and the tray while the hot members are touching against the filmon the portion of the flange of the tray.
 20. A packaging apparatus, inwhich a tray provided with a flange and an opening surrounded by theflange on its upper face and containing an article to be packaged, iscovered with a film over the opening and the film is welded to theflange, the packaging apparatus comprising: a hot member having a facethat is capable of touching against the film on a portion of the flangeof the tray, the face capable of touching the film being at an anglewith respect to a horizontal plane; and moving means for moving at leastone of the hot member and the tray while the hot member is touchingagainst the film on the portion of the flange of the tray to form athermally welded portion; and a controller that controls the movingmeans to move at least one of the tray and the hot member so that thefilm spanning the opening is thermally cut at the outside of thethermally welded portion while being thermally welded to the tray.
 21. Apackaging apparatus, in which a tray having on its upper face a flangeand an opening that is surrounded by the flange and containing anarticle to be packaged is covered with a film over the opening with thefilm being welded to the flange, the packaging apparatus comprising: asupport member arranged to support the tray with a portion of the flangelying in a first plane that substantially contains the film when weldedto the flange; a hot member having a face arranged and configured totouch against the film on a portion of the flange of the tray, the facebeing arranged to be lying in a second plane that forms an angle withrespect to the first plane when touching; and a hot member movingmechanism that moves the hot member along the flange while the hotmember is touching against the film on the portion of flange of thetray.